Characterisation of silicon photonics devices

Silicon based integrated circuits has been dominating the electronics technology industry in the last few decades. As the telecommunications and the computing industry slowly converges together, the need for a material to build photonics integrated circuits (PIC) that can be cost-effective and be produced in mass market has become very important. This thesis describes and outlines the characteristics of high index contrast waveguides as a building blocks that can be designed, fabricated and employed on devices in silicon photonics. Initially in this work, a fully vectorial H-field based finite element method has been used to obtain the modal characteristics of high index contrast bent waveguide to get a better understanding of the curved section. Through the beam propagation method, the propagation losses and the spot-size along the propagation distance are obtained when a mode from the straight guide is launched into a bent guide. It is also learnt that mode beating exists at the junction of a straight-to-bent waveguide, in which higher order modes will also be generated. It will be shown in this work that power do exchange between the two polarization states, therefore the polarization conversion, the power losses and the bending losses will be investigated. It will also shown in here that by applying lateral offsets with coupled waveguides of unequal widths, the insertion loss can be reduced. Secondly, for a high index contrast waveguide such as the silicon strip waveguide with a nanoscale cross-section, modes in such waveguide are not purely TE or TM but hybrid in nature, with all the six components of their E and H-fields being present. Therefore a detail analysis of the modal field profiles along with the Poynting vector profile will be shown. The effects of waveguide's width and height on the effective indices, the hybridness, the modal effective area and the power confinement in the core or cladding has been studied. Furthermore the modal birefringence of such strip waveguide will be shown. It will be presented that for a strip waveguide with height of 260 nm, single mode exists in the region of the width being 200 nm to 400 nm and that the modal effective is at its minimum when width is around 320 nm for both polarization states. Thirdly, a compact polarization rotator with an asymmetric waveguide structure design, suitable for fabrication that does not require a slanted side wall or curved waveguide is considered in this work. It will be shown in here that due to the hybrid nature of the asymmetric waveguide design, maximum polarization rotation (from TE to TM) will be achieve by enhancing the non-dominant field profile of both polarized fundamental mode. As the modal hybridness and the propagation constants of both polarized modes will be obtained, the half-beat length, polarization conversion and polarization cross-talk will be calculated by using the FEM and the least squares residual boundary method (LSBR). It is learnt that a compact single stage polarization rotator with a device length of 48 μm with more than 99% of polarization conversion is achieved in this work. Finally, a study of vertical and horizontal slot waveguide will be shown. Based on silicon strip waveguide, a detail modal characteristics of E and H-fields along with the Poynting vectors are presented. It will be shown that for slot waveguide, high power confinement and power density will be achieved in the slot area. It will be presented that by optimising the waveguide and slot dimension, the performance of the power confinement and power density in the slot region can be improved

A rotating ring-disk study of interactions among SPS, cuprous ions, and oxygen

The most common additives in copper plating baths for deep via filling are chloride, polyethylene glycol (PEG), a suppressor, and bis-(3-sulfopropyl)-disulfide (SPS), an accelerant. The copper in acid plating baths is provided by a Cu (II) salt. Cu (I) may be present as well and it influenced the effectiveness of SPS. In this investigation, the interactions among SPS, Cu (I) and oxygen were studied by rotating ring-disk voltammetry. The ring electrode acted as a plating substrate, while Cu (I) was generated at the disk by anodic dissolution of copper. Because Cu (I) is consumed by reaction with oxygen, the experiments were carried out under air, oxygen, or argon atmospheres. When SPS is present in the solution, a sudden kinetic acceleration is observed at the ring during Cu (I) generation at the disk. By comparing the ring deposition rate without and with Cu (I) generation at the disk, it is found that deposition is accelerated by higher levels of Cu (I) and SPS. The result is considered in light of the hypothesis that the true accelerant is formed by homogeneous reaction of SPS and Cu (I)

Characterisation of silicon photonics devices

Silicon based integrated circuits has been dominating the electronics technology industry in the last few decades. As the telecommunications and the computing industry slowly converges together, the need for a material to build photonics integrated circuits (PIC) that can be cost-effective and be produced in mass market has become very important. This thesis describes and outlines the characteristics of high index contrast waveguides as a building blocks that can be designed, fabricated and employed on devices in silicon photonics. Initially in this work, a fully vectorial H-field based finite element method has been used to obtain the modal characteristics of high index contrast bent waveguide to get a better understanding of the curved section. Through the beam propagation method, the propagation losses and the spot-size along the propagation distance are obtained when a mode from the straight guide is launched into a bent guide. It is also learnt that mode beating exists at the junction of a straight-to-bent waveguide, in which higher order modes will also be generated. It will be shown in this work that power do exchange between the two polarization states, therefore the polarization conversion, the power losses and the bending losses will be investigated. It will also shown in here that by applying lateral offsets with coupled waveguides of unequal widths, the insertion loss can be reduced. Secondly, for a high index contrast waveguide such as the silicon strip waveguide with a nanoscale cross-section, modes in such waveguide are not purely TE or TM but hybrid in nature, with all the six components of their E and H-fields being present. Therefore a detail analysis of the modal field profiles along with the Poynting vector profile will be shown. The effects of waveguide's width and height on the effective indices, the hybridness, the modal effective area and the power confinement in the core or cladding has been studied. Furthermore the modal birefringence of such strip waveguide will be shown. It will be presented that for a strip waveguide with height of 260 nm, single mode exists in the region of the width being 200 nm to 400 nm and that the modal effective is at its minimum when width is around 320 nm for both polarization states. Thirdly, a compact polarization rotator with an asymmetric waveguide structure design, suitable for fabrication that does not require a slanted side wall or curved waveguide is considered in this work. It will be shown in here that due to the hybrid nature of the asymmetric waveguide design, maximum polarization rotation (from TE to TM) will be achieve by enhancing the non-dominant field profile of both polarized fundamental mode. As the modal hybridness and the propagation constants of both polarized modes will be obtained, the half-beat length, polarization conversion and polarization cross-talk will be calculated by using the FEM and the least squares residual boundary method (LSBR). It is learnt that a compact single stage polarization rotator with a device length of 48 μm with more than 99% of polarization conversion is achieved in this work. Finally, a study of vertical and horizontal slot waveguide will be shown. Based on silicon strip waveguide, a detail modal characteristics of E and H-fields along with the Poynting vectors are presented. It will be shown that for slot waveguide, high power confinement and power density will be achieved in the slot area. It will be presented that by optimising the waveguide and slot dimension, the performance of the power confinement and power density in the slot region can be improved.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Controlling Electromagnetic Fields with Tensor Transmission-Line Metamaterials.

The advent of metamaterials and transformation electromagnetics have revolutionized the use of materials in the control of electromagnetic fields. Metamaterials enabled the control of material properties, and transformation electromagnetics provided a systematic procedure for designing these materials to achieve a specified electromagnetic field distribution. Greater control over the material parameters amounts to greater control over electromagnetic fields. In particular, the ability to design anisotropic materials with spatially varying material parameters is crucial to the development of countless novel guided-wave and radiating structures. This thesis shows how to develop electromagnetically anisotropic, inhomogeneous materials using circuit networks: tensor transmission-line metamaterials. Tensor transmission line metamaterials are circuit-based metamaterials possessing tensorial effective material parameters. They are magnetically anisotropic, and their anisotropic material parameters consist of a 2×2 permeability tensor and scalar permittivity. A theoretical basis for analyzing, synthesizing and homogenizing tensor transmission-line metamaterials is developed. Their propagation characteristics are verified through full-wave simulation and experiment. In addition, a distinct method for arbitrarily controlling the phase progression and power flow of electromagnetic fields within a region of space is proposed. The method provides an alternative design approach to transformation electromagnetics, and it exploits an anisotropic medium’s ability to support power flow and phase progression in different directions. The proposed method has proven useful in establishing aperture field profiles with arbitrary phase and amplitude distributions. Illustrative examples are introduced. Beam-formers, which can create arbitrary aperture field distributions (phase and amplitude) are reported.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108824/1/ggok_1.pd

Electromagnetic Wave Theory and Applications

Contains table of contents for Section 3, reports on four research projects and a list of publications.National Aeronautics and Space Administration Grant NAGW-1617National Aeronautics and Space Administration Agreement 958461National Aeronautics and Space Administration Grant NAGW-1272U.S. Army Corp of Engineers Contract DACA39-87-K-0022U.S. Navy - Office of Naval Research Grant N00014-89-J-1107U.S. Navy - Office of Naval Research Grant N00014-92-J-1616Digital Equipment CorporationJoint Services Electronics Program Contract DAAL03-92-C-0001U.S. Navy - Office of Naval Research Grant N00014-90-J-1002U.S. Navy - Office of Naval Research Grant N00014-89-J-1019U.S. Department of Transportation Agreement DTRS-57-88-C-00078TTD13U.S. Department of Transportation Agreement DTRS-57-88-C-00078TTD30U.S. Department of Transportation Agreement DTRS-57-92-C-00054TTD1DARPA/Consortium for Superconducting Electronics Contract MDA972-90-C-0021National Science Foundation Fellowship MIP 88-5876

Silicon nitride waveguide optical filter components for access network applications

Silicon nitride (SiN) waveguide based micro ring/racetrack resonators to be used as filters in the Chirp Managed Lasers (CMLs) are modelled and demonstrated over the standard silicon (Si) wafer. The development of these racetrack-resonators, with a narrow free spectral range (FSR) of 100GHz is in correspondence to the international telecommunication union (ITU) recommended channel grid spacing required for the latest next generation passive optical networks (NGPON2) systems. The study of such optical filters, which tend to increase the transmission range of the directly modulated laser (DML) signal, is motivated from the research and development directed towards bringing the CMLs to a reality. Also, a single SiN ring resonator and a silicon waveguide based cascaded 3-ring design, both integrated within the Y-splitter configuration are presented to be used as a reflector in external cavity laser. These ring reflectors are designed to have a broad FSR, which is achieved using the Vernier effect by serially coupling three racetrack resonators. In this thesis, we analyze and optimize the optical response of the above mentioned devices based on SiN waveguides deposited over silicon wafers. The design parameters are optimized based on analytical modelling and simulations are carried out with finite difference time domain (FDTD) solver. The devices are fabricated in different labs and clean room facilities within Montreal in collaboration with our industrial partner AEPONYX. The performance of these fabricated devices is characterized using an optical test setup in university lab facilities. The simulation and the measurement results are in close proximity for a large 4-port add-drop racetrack resonator, giving a FSR close to 100GHz specified for the NGPON2 systems and an extinction ratio (ER) of >15 dB to be useful for modulating the inherent chirp of the directly modulated lasers (DML) and thereby increasing the transmission range of the data signals. For the Si waveguide based cascaded 3rd order ring reflector, a wide FSR of 90.2 nm is achieved numerically and a FSR of around ~6.02 nm is demonstrated for the SiN single ring reflector experimentally which is in close proximity to the theoretical value of 6.2 nm

Advanced materials, process, and designs for silicon photonic integration

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Includes bibliographical references (p. 229-235).The copper (Cu) interconnect has become the bottleneck for bandwidth scaling due to its increasing RC time constant with the decreasing gate line width. Currently, silicon based optical interconnect is widely pursued as the most promising technology to replace Cu in microprocessor chips. Silicon optical interconnect is based on integrated silicon nanophotonic technologies. It can leverage the large scale and low cost of CMOS technology and deliver higher bandwidth with no EMI and low heat dissipation. Passive photonic component, such as waveguides, couplers, filters, splitters, are the backbone of integrated photonic circuit. This thesis is dedicated to the development of low loss, high performance, high index contrast optical waveguides and couplers via materials, processes engineering, development, and device designs. We primarily focus on SOI single crystalline silicon (c-Si or SOI), PECVD amorphous silicon (a-Si:H, or simplified as a-Si), and PECVD silicon nitride (SiNxHy) based single mode channel waveguides.We have previously identified that sidewall roughness scattering is the dominant loss mechanism for the TE mode in high index contrast single mode channel waveguides. In this thesis, we provide a comprehensive understanding of the roughness scattering and its positive correlations with (1) sidewall optical intensity; (2) sidewall RMS roughness; and (3) sidewall index contrast. Novel processes and designs, such as hard mask and chemical oxidation, are developed based on the above understanding. In single mode, 500 x 200 nm2 c-Si channel waveguides, we have achieved world-record 2.7 dB/cm and 0.7 dB/cm transmission loss coefficients for the TE mode and the TM mode, respectively.For deposited waveguides, bulk absorption loss is also important for both TE and TM modes.For PECVD a-Si, we adapt hydrogen passivation to reduce dangling bond density.(cont.) We also use a thin silicon nitride as the over cladding layer to help preserve H passivation and to reduce sidewall index contrast, acting as the graded index layer for a-Si waveguide core. We have accomplished the lowest reported loss coefficients in directly etched, single mode, 700 x 100 nm2 a-Si channel waveguides of 2.7 dB/cm for the TE mode, comparable to c-Si waveguide with similar dimensions. For the first time, damascene process has also been demonstrated as a promising process for a-Si waveguide fabrication. We have achieved a record-low loss of 2.5 dB/cm in 600 x 100 cm2 a-Si channel waveguides. Chemical-mechanical polishing (CMP) is the most critical step.For PECVD SiNxHy, we have previously identified that the absorption loss is due to the resonant absorption caused by N-H vibration. In this thesis, three different low temperature approaches have been developed and optimized to reduce NH concentration in as-deposited SiNxHY via (1) deposition chemistry; (2) post-deposition Ultraviolet light (UV) treatment; and (3) post-deposition, in-situ N2/Ar plasma treatment. All three processes are compatible with CMOS back-end processes, such as a-Si process. While changing deposition chemistry is the simplest method to obtain low NH containing SiNxHy, it comes with high SiH concentration and may have undesirable properties. Experimentally, for UV treatment, the highest H removal percentage is 60%; for plasma treatment, - 90%. UV treatment shows strong compositional dependence. The underlying mechanism of such dependence is identified and confirmed by Monte-Carlo modeling. Low loss and spectrally broadband optical couplers are indispensable optical components in an integrated photonic circuit. A high performance coupler should be capable of overcoming the mode-size mismatch, mode-shape mismatch, mode-position mismatch, and polarization mismatch, bridging different optical devices with minimal coupling loss. In this thesis, we have demonstrated a fiber-to-waveguide coupler based on asymmetric graded index taper and monolithically integrated cylindrical lens.(cont.) It is capable of transforming single mode light between single mode fiber and waveguides with minimal coupling loss of 0.45 dB between 1520 nm and 1630 nm. We have also demonstrated a vertical waveguide-to-waveguide coupler that is based on complementary inverse tapers. This design is tolerant of large refractive index mismatch between the two waveguides and also of any fabrication variation that would affect the effective indices of the two waveguides. We have achieved a minimal coupling loss of 0.25 dB per coupler and excellent broadband behavior is also demonstrated. Slot waveguides are a newly developed class of waveguides with unique optical properties. Slot waveguides can achieve exceptional high optical field in nanometer sized low index regions. In this thesis, we have demonstrated low loss transmission of 6 dB/cm for the fundamental slot mode in horizontal slot waveguides at 1550 nm. The horizontal slot configuration removes the constraints of thin slot definition by lithography and allows an arbitrarily thin slot to be fabricated via deposition or oxidation. Because the resulting interface is much smoother than the etched interface, the transmission loss in horizontal slot waveguides is much lower than in vertical slot waveguides. We also demonstrated that multiple slot configurations result in higher optical confinement compared to single slot configurations with the same slot thickness. The low loss and high optical confinement in the low index slot region realized in horizontal slot waveguides promises many useful applications, such as Er-doped silicon-based light emitters. For integration of slot waveguides with conventional channel waveguides, we have designed and simulated mode couplers and polarization rotators for slot-slot, slot-channel waveguide mode transformations.Athermal operation is important for realizing stable passive, WDM optical network on silicon. Athermal design of silicon waveguide systems uses advanced polymer cladding of large negative TO coefficient to provide compensation for the large positive TO coefficient in silicon. The reduced thermo-optic (TO) effect is experimentally demonstrated by reducing TO coefficient from 85 pm/K to 11 pm/K using polymer films.by Rong Sun.Ph.D

Design of Power-Efficient Optical Transceivers and Design of High-Linearity Wireless Wideband Receivers

The combination of silicon photonics and advanced heterogeneous integration is promising for next-generation disaggregated data centers that demand large scale, high throughput, and low power. In this dissertation, we discuss the design and theory of power-efficient optical transceivers with System-in-Package (SiP) 2.5D integration. Combining prior arts and proposed circuit techniques, a receiver chip and a transmitter chip including two 10 Gb/s data channels and one 2.5 GHz clocking channel are designed and implemented in 28 nm CMOS technology. An innovative transimpedance amplifier (TIA) and a single-ended to differential (S2D) converter are proposed and analyzed for a low-voltage high-sensitivity receiver; a four-to-one serializer, programmable output drivers, AC coupling units, and custom pads are implemented in a low-power transmitter; an improved quadrature locked loop (QLL) is employed to generate accurate quadrature clocks. In addition, we present an analysis for inverter-based shunt-feedback TIA to explicitly depict the trade-off among sensitivity, data rate, and power consumption. At last, the research on CDR-based​ clocking schemes for optical links is also discussed. We introduce prior arts and propose a power-efficient clocking scheme based on an injection-locked phase rotator. Next, we analyze injection-locked ring oscillators (ILROs) that have been widely used for quadrature clock generators (QCGs) in multi-lane optical or wireline transceivers due to their low power, low area, and technology scalability. The asymmetrical or partial injection locking from 2 phases to 4 phases results in imbalances in amplitude and phase. We propose a modified frequency-domain analysis to provide intuitive insight into the performance design trade-offs. The analysis is validated by comparing analytical predictions with simulations for an ILRO-based QCG in 28 nm CMOS technology. This dissertation also discusses the design of high-linearity wireless wideband receivers. An out-of-band (OB) IM3 cancellation technique is proposed and analyzed. By exploiting a baseband auxiliary path (AP) with a high-pass feature, the in-band (IB) desired signal and out-of-band interferers are split. OB third-order intermodulation products (IM3) are reconstructed in the AP and cancelled in the baseband (BB). A 0.5-2.5 GHz frequency-translational noise-cancelling (FTNC) receiver is implemented in 65nm CMOS to demonstrate the proposed approach. It consumes 36 mW without cancellation at 1 GHz LO frequency and 1.2 V supply, and it achieves 8.8 MHz baseband bandwidth, 40dB gain, 3.3dB NF, 5dBm OB IIP3, and −6.5dBm OB B1dB. After IM3 cancellation, the effective OB-IIP3 increases to 32.5 dBm with an extra 34 mW for narrow-band interferers (two tones). For wideband interferers, 18.8 dB cancellation is demonstrated over 10 MHz with two −15 dBm modulated interferers. The local oscillator (LO) leakage is −92 dBm and −88 dB at 1 GHz and 2 GHz LO respectively. In summary, this technique achieves both high OB linearity and good LO isolation

Holographic optical interconnects in dichromated gelatin

Abstract unavailable please refer to PD